Ok I'm going to create a new Wallet one of these days and encrypt it.
I plan to use these steps (with 0.15.1):

1) rename wallet.dat to oldwallet.dat
2) launch Bitcoin-QT shortcut (that is pointing to the datadir that now doesn't have a wallet.dat name) --> i think this should create a new HD wallet
3) encrypt new wallet --> restart bitcoin --> copy the new address --> backup new encrypted wallet --> quit bitcoin-qt
4) rename new wallet to walletnew.dat / rename oldwallet.dat back to wallet.dat
5) send the bitcoins (maybe in 2 tx, maybe just in 1) --> quit bitcoin-qt
6) rename walletnew.dat to wallet.dat (put my old wallet somewhere...)
7) start bitcoin-qt and wait for the balance to arrive.